Magnesium hydroxide in slurry form is useful as a pumpable source of magnesium hydroxide for various chemical processes, including but not limited to the following: (1) pH adjustment, including waste acid and acidic wastewater neutralization; (2) wastewater treatment, including precipitation of heavy metal contaminants; (3) scrubbing and neutralization of acidic vapors in flue gases or process off-gases; and (4) production of specialty magnesium compounds (e.g. MgSO.sub.4, MgNO.sub.3, MgCl.sub.2, etc.) as a source of magnesium.
By providing magnesium hydroxide in slurry form of at least moderate quality, capital extensive and potentially dangerous (due to the hydration exotherm) MgO powder slaking operations are eliminated for the end user. Magnesium hydroxide slurries of such quality have additional advantages including the ability to be easily handled and stored, and the ability to be reliably dosed to chemical processes as desired. In fact, such magnesium hydroxide slurries can be transported to the point of application and stored for time periods of days to several weeks under intermittent to constant agitation without incurring adverse effects such as settling of solids and excessive viscosity.
Lower quality atmospheric hydrated magnesium hydroxide products produced from burnt natural magnesite are common, but in many cases do not have the above desirable characteristics and can cause numerous processing difficulties including the following: product inhomogeneity; obstruction of transport pipelines, valves, processing equipment and storage equipment; formation of an impacted bed of non-pumpable magnesium hydroxide solids at the bottom of storage tanks and process vessels; inconsistent or insufficient feed rate to processes; excessive energy costs for transporting/pumping the product; and high maintenance costs for systems incorporating the product.
At present, however, the only moderate to high quality magnesium hydroxide slurries available are believed to be synthetic magnesium hydroxide products produced from the soluble magnesium present in brine fields and seawater. For economic reasons, these synthetic magnesium hydroxide slurries are generally produced in close proximity to sources of brine or seawater.